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    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        // Object.prototype.age = 30;
        // function Person() {
        //     this.age = 10
        // }
        // Person.prototype.age = 20;
        // let zhangsan = new Person()
        // console.log(zhangsan.age)
        // Object.prototype.age = 10
        // let obj = {
        //     name: "汪汪汪",
        //     age: 21
        // }
        // Object.setPrototypeOf(obj, { height: "178cm" })
        // for (let key in obj) {
        //     if (obj.hasOwnProperty(key)) {
        //         console.log(key)
        //     }
        // }
    </script>
</body>

</html>